System and apparatus for the electric recording and reproducing of sound



Sept. 15, 1931. M. H. LOUGHRIDGE 1,822,932

SYSTEM AND APPARATUS FOR THE ELECTRIC RECORDING AND REPRODUCING OF SOUND Filed Nov. 2, 1928 A TTORNE Y.

Patented Sept. 15, 1931 UNITED rr MATTHEW H. LOUGHRIDGE, OF BOGrOTA NEW JERSEY SYSTEM AND APPARATUS FOR THE ELECTRIC RECORDING AND REPRODUCIN'G OF SOUND App1ication filed. November 2, 1928. Serial No. 316,855.

This invention relates to sound recording and reproducing apparatus and amplifying means used in connection therewith. It embodies a system for transmitting electrical vibrations corresponding to sound Waves, amplifying these transmitted vibrations and reproducing them in amplified form either through an audible device, or on a mechanically inscribed record. This invention provides for transmitting sound from a microphone through an amplifier, transcribing this sound mechanically on a phonograph record and then reproducing the sound from the record by a magnetic pick up, passing the electrical impulses thus generated through the amplifier and reproducing the results on a loud speaker. The magnetic pick up is provided with a recording and a reproducing stylus either of which are brought into active operation by a movement of the pick up head. This movement also sets up the particular circuit connections required to the stylus that is to be used.

The objects of the invention are to simplify a system of this kind, to make it instantly adaptable for recording or reproducing sound and'to adapt it to portable units. Other objects of the invention will appear from the following specification and the accompanying drawings, in which, Fig. 1 is a diagram of the operating circuits that may be used in carrying out my invention, Fig. 2 is a side elevation of a phonograph turntable with a record and a stylus head, Fig.

3 is a diagram of thecircuit controller and the connections to the associated apparatus, Fig. 4 is an elevation of a form of mechanical amplifier that may be used with this inven tion, Fig. 5 is one type of stylus head that may be used for the magnetic pick up and Fig. 6 is a detail of Fig. 5.

The amplifying mechanism comprises the motor 11 driven from the mains 12 and through shaft 13 of the armature the generatorsA, B and C are driven. A is a multipolar D. C. generator provided with field coils 18 and a rotating armature 19. The field is made from laminated sheets as indicated in Fig. 4 and is energized by the circuit of wires 14 and 15 and the battery 16, the voltage of which is regulated by the adjustable resistance 164.

It is apparent that as armature 19 rotates direct current is generated in the circuit 2021 which is the product of the current in circuit 1415 and the mechanical energy supplied to the armature 19 through the shaft 13. Current is thus delivered to wires 20-21 of the same character as the current in wires 1415 but amplified by the generator A.

B is a multipolar generator similar in all respect to generator A but much larger. This generator is provided with field coils 22 connected in circuit with wires 2021 so that the field is energized by the amplified current from generator A. The armature 231as it is rotated by shaft 13 generates adirect current in the circuit of wires 2l25 which is the product of the mechanical energy supplied to the armature and the current in the field coils and hence this current is amplified over the current in wires 2021 while it. retains the characteristic of the original current in Wires 1415.

v In the same way, the generator C is larger than generator B but otherwise is similar in operation and its field coils 26 are energized by the current in wires 2425 so that the armature 27 generates a current inthe circuit of wires 2829 which is the product of the current in the field coils and the mechanical energy supplied by motor 11.

It will be notedthat the circuit of wires 1415 represent the input circuit and the circuit of wires 2S29 represent the output circuit which has all the characteristics of the input circuit in increased volume. Thus the devices A, B and C represent a three stage amplifying unit and while the mechanical amplifier described is the preferred type,

it should be understood that the system is operable with the well known type of electron amplifiers.

Mechanical amplifiers of the type described have been proposed for amplifying telephone circuits in the past. One difficulty attending the use of this device arose from the hum produced in'the armature circuit as the commutator bars moved under the brushes chang ing the circuit from one coil of the armature to the next coil. In the present application I eliminate the harmful effects of this hum by increasing its frequency to the point where it becomes inaudible. This is secured by using a motor running at high speed to drive the armatures of the multipolar generators at high speed, by the sets of brushes on each armature commutator for each pair of poles and by so placing the brushes on the commutators that they pass over the insula tion between the commutator bars at. diiferent times on each armature and on the armature of each generator. The speed at which commercial motors of the type proposed run is approximately 4,500 B. P. M. In this manner the hum is easily subdivided until it has a frequency exceeding 20,000 per second and is therefore inaudible and harmless. The principles of this amplifier are disclosed in my co-pending application, Serial No. 576,821, filed July 22, 1922.

In practice the generator A is verysmall and its magnetic field is highly sensitive 'to the current in wires 14 and 15. It is thus readily influenced by feeble currents. The entire amplifying unit A, B, and 'C with the motor 11 as indicated in Fig. 4 is small and compact, is readily portable and always usable where an electric supply is available.

A double acting microphone is indicated by '40 connected in circuitwith wires 42 and 43 and the battery 41. The wires 42 and 43 connec't through the double :pole, double throw switch 44 with the transformer coil 45., the centre of which connects to the battery 41. As the microphone is used a circuit is established from the battery to wire 42 including one side of coil 45, or wire 43 including the other side of coil 45, thus energizing coil 45 according to the sound vibrations in front of the microphone.

The coil 17 is inductively coupled with "coil 45 and receives the electrical impulses from the microphone which are superimposed on the circuit of wires 14-15 and the field of generator A and through the amplifying system these impulses appear in an amplified form in the circuit of wires 28-29, that is, the output circuit of the amplifier.

Ilhrough the double pole, double throw switch 30, the wires 28-29 are connected by wires 31-32 with the loud speaker 33 which au'di'bly reproduces the sounds transmitted by the microphone.

37 represents the operating coil of a :mag- -netic pick up device as used on the phonographic record 38 through the stylus 39. This record is preferably of the type adaptable for recording and reproducing as for instance, the metallic record made according to the process disclosed in the WV-adsworth Patent 1,421,045, ofJune 27, 1922. As soon as a record made by this process is finished, it is immediately ready for reproduction.

With the switches 30 and 44 in the position shown it will be noted that the microphone 40 is disconnected and the coil 37, through the wires 3536 and switch 44 connects to coil 45 and through 17 and the amplifying used with this invention isshown in Fig. 5.

A pair of magnets 71 and 72 are provided with pole pieces 75 which support the operating coil 37 and the fiat spring 76 carrying the armature 77 which is held centered by this spring between the ends of the magnets as shown but which is free to vibrate either by electrical impulses from the coil 37, or by impulses from the stylus 79 secured in the chuck 78 as it engages the undulations of a record groove. The magnets 71 and 72 are held in place by the clamp 73.

The armature 7 7 is free to vibrate in the magnetic field of magnets 71 and 72. If it is vibrated by the stylus 79 it generates a current in coil 37-011 the principle of a motor generator and, on the other hand, if electrical impulses are applied to coil 37. the stylus 79 will be vibrated in response to said impulses. The magnetic pick up is thus reversible in its function and will record electrical impulses received, or reproduce the electrical impulses by which a record is inscribed.

The stylus used for recording is usually different from the reproducing stylus. The former is harder and is designed to cut or impress the sound groove in the record while the latter is softer and is designed to pass over the record grooves without material injury to these grooves. For this purpose I provide a recording and reproducing stylus ineach magnetic pick up, either one of which may be brought into use as desired. 'The flat spring 76 is provided with an aperture 80 to receive the recording stylus 56, Fig. 2 and with another aperture 81'to receive the reproducing stylus 57. Each of the needles 56 and 57 are vibrated by the armature 7 7.

In Fig. 2, a feed screw 51 is suitably driven by the phonograph mechanism which drives the turntable 59. The stylus arm 52 is fed across the turntable by the screw 51 with the stylus 56 engaging the record 58. The pressure by which the stylus engages the record is regulated by the sliding weight 53 and is usually greater when recording than when reproducing. The pick up head 55 connects to arm '52 by a socket connection 54 in which it may be rotated through and latched in position by the latch 54a. It will be noted that when this head makes a half turn, the stylus 56 is removed from engagement with the record and the stylus 57 is brought into active operation. The upper end of the stylus head terminates in a rotary circuit controller 60 engaged by contact fingers 61 insulated from and supported by the arm 52.

The circuit controller 60 is arranged to accomplish automatically, as the stylus head is changed, the purposes of switches 30 and 44. This is shown in detail in the circuit diagram, Fig. 3. The drum is provided with contact plates 62, 63, 64 and 65 engaged by the contact fingers as shown. In the position illustrated the coil 37 is connected to the transformer coil 45 and the microphone 40 is disconnected; also the loud speaker 33 is connected to wires 28-29 of the generator C. This is the reproducing position. WVhen the pick up head is rotated to bring the other stylus into engagement with the record, the coil 37 is disconnected from 45 and is connected to wires 28-29, the loud speaker 33 is disconnected and the microphone 40 is connected to coil 45. This is the recording position.

This invention may be used for reproducing commercial phonograph records, for recording phonograph records and immediately reproducing them and for amplifying graph record. The invention can be carried out by apparatus a large part of which is commercial stock.

This invention can be applied in a variety of ways by those skilled in the use of electrical apparatus and includes a full range of equivalents and alternatives.

Having thus described my invention, I claim: I

1. In a system as described, the combination, a phonograph record, a stylus head having a recording and a reproducing stylus, means whereby said head may be moved to bring either of said recording or reproducing stylus into engagement with said record, an electrically operated device controlling said stylii, an amplifying system having an input circuit and an output circuit and means operated by said head for connecting said device with said input circuit when the reproducing stylus engages the record and for connecting said device with said output circuit when the recording stylus engages the record.

2. In a system as described, the combination, a phonograph record, a stylus head having a recording stylus and a reproducing stylus, means whereby said head may be moved to bring either of said stylii into engagement with said record, said head comprising a device moving in a magnetic field and operatively connected with said stylii, an amplifying system connected with said device andv a switch operated by said h eadv control- :ling the connectionsbetween said device and said amplifying system. 1

3. In a system asdescribed, the combination, a phonograph'record, a stylus head comprising a magnetic field, a member vibrating ln'said field, a recording stylus and a reproducing stylus operatively connected with said member, a coil of wire located in said magnetic field,.means forbringing either'ofsaid V styliiinto engagement with said record and for automatically controlling the circuit. of

said coil and atranslatingdevice connected with said coil. 4. In a system for reproducing sound, the

combination, a translating device for receiving sound vibrations and translating them into. electrical effects, an amplifying system comprising a plurality .ofv motor generators progressively increasing in size and having their armatures driven from an exteriorsource of power, the first generator being smallto respond to feeble impulses, a circuit for energizing the field of the first generator controlled by the effects from said1translating device and the armature circuit of this generator energizingthe'field ofthe next sized generator, and so on repeating these connections between-each progressive size of generator and means connecting the armature of the last generator with a-sound pro ducing device. 1 sound without the intervention of the phonointo electrical effects, an amplifying system comprising a plurality of direct current motor generators increasing in size having the1r armatures connected on the same shaft and: driven at high speed from an exteriorsource of power, a circuit for energizing the field of the first generator controlled by the effects from said translating device, the armature circuit of this generator energizing the field of another generator and the armature circuit of the last generator connected with a sound producing device whereby fluctuations in the circuits of said generators caused by said generators are increased in frequency in the output circuit of the last generator.

6. An amplifying system for amplifying electrical impulses comprising a plurality of motor-generators having their armatures and commutators connected on the same shaft, a motor driving said shaft at a comparatively high speed, an input circuit for the first generator energizing its field with direct current, the output circuit from the commutator of this generator energizing the field of the next generator and so on for the series whereby fluctuations in the circuits of said generators caused by said generators are increased in frequency in the output circuit said output circuit connected with a translating device iorproducing. soundin response to current variations'and means for impressing the current impulsesto be amplified upon the first input circui.

7 An ampliztying system for amplifying electrical impulses comprising a plurality of motor.generators having their armatures and commutators connected on the same shaft, :1

motor driving said shaft at a comparatively high speed an input circuit for the first gen-- ierator energizing its field with: direct current, the output circuit from the commutator of this generator energizing the field of the next generator and so on for the seriesi the COlIllHlllliLtOl'S of each generator being adjusted relative to their brushes to interrupt the circuit between the bars of the commutators at different times whereby the bum produced by the commutators is increased in frequency and the output circuit from the commutator of the last generator connected with a translating device for producing sound in response to current variations and means for impressing the current impulses to be amplified upon the first input circuit.

8. An'ia'mpli-fier system for amplifying an electric circuit with feeble current, compris- 7 ing :a plurality of motor generators progressively increasing in size and having their armatures driven from an exterior source of power, said c1rcu1t being connected WLth the smaller of said generators and the output of this generator being connected with the next sized generator and so on, repeating these connections between each progressive size of generator and a translating dew-ice connected with the output circuit of the last grenerator.

In testimony whereof I .affixmy signature.

MATTHEW H. LOUIGHBIDGE, 

